GB2142009A - N,n,n',n'-tetra (hydroxyethyl)-5-acetylamino-2,4,6-triidoisophthaloyldiglycinamide - Google Patents

Description

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GB2 142 009A

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SPECIFICATION

N, N, N', N '-tetra(hyd roxyethyl)-5-acetylamino-2,4,6-triiodoisophtaloyl-diglyci-5 namide, a process for the preparation of said compound and an X-ray contrast agent containing said compound.

The invention relates to the new water soluble 10 nonionic compound N,N,N',N'-tetra(hydroxye-thyl)-5-acetylamino-2,4,6-triidoisophtaoyl-di-glycinamine, to a process for the preparation of said compound and to an X-ray contrast agent containing said compound. Water sol-15 uble, nonionic compounds constitute a new development in the field of radiodiagnostics.

Aqueous solutions of the non-toxic salts of triidobenzoic acid derivatives, used for e.g. angiography and urography, are well-known. 20 Generally these solutions are well tolerated and have a low toxicity. A disadvantage however is the high osmolality in the required diagnostic concentration, which is a multiple of the osmolality of blood and which may 25 cause undesired side-effects. Half of the osmolality originates from ions that are indispensable for the solubility, but no not contribute to the contrast activity.

So the search for new compounds was 30 started, of which aqueous solutions could be prepared of the required iodine content but in lower molar or ionic concentrations.

Thus, compounds of the ionic type were synthesized, consisting of two triidobenzene 35 moieties and one acidic function. On salification of such a hexaiodo mono acid with meglumine or sodium, an average of three iodine atoms per dissolved particle is obtained, and the molar concentration is only half of same of 40 the comparable triidobenzoates. Examples of this type are described in the Swiss patent specification No. 607 995.

Also triiodinated bases were prepared and combined with the conventional triidobenzoic 45 acids as described in the European patent specification No. 0022744. In the salts thus obtained, both cation and anion contribute to the contrast activity and the ballast of sodium and/or meglumine is avoided.

50 Water soluble nonionic compounds have been prepared as described in the British patent specifiction 13121591 and 1472050 and the U.S. patent specification 4021481. The presence of a number of hydroxyl groups 55 plays a decisive role in the hydrophylic character and water solubility.

Examples are:

N-(N-methyl-3,5-doacetylamino-2,4,6-triio-dobenzoyl)-glucamine, [metrizamide]; 60 N,N'-bis(1,3-dihydroxypropyl)-5-lactylamino-2,4,6-triiodoisophtalamide [iopamidol]; N,N'-bis(2,3-dihydroxypropyl)-5-[N-(2,3-dihy-droxypropyl)acetyl-amino]-2,4,6-triiodoiso-phtalamide [iohexol],

65 Water soluble and nonionic dimer compounds are also described, consisting of two triiodeobenzene moieties, thus containing six iodine atoms per molecule. Their application is however limited because of the high viscosity of their solutions.

The use of iodine compounds with low osmolality is an important improvement in radiography. A disadvantage however is the rather high cost of these compounds, if compared with the conventional contrast agents. This can easily be understood, because the manufacturing procedure comprises more steps and the raw materials are generally more expensive. Apart from this, the isolation and final purification require more effort in connection with the high solubility in water.

The present invention relates to a new water soluble nonionic compound, that can be prepared in the required purity in a simple way at relatively low cost.

This compound is:

N, N, N', N '-tetra(hydroxyethyl)-5-(acety la m ino-2,4,6-triiodoisophtaloyl-bis(glycinamide)

I CONHCH.CON (CH.OH)

* / * a 2

CHjCONH-^QNi r~£ CONH CHACON (CJ^OH),

Similar derivatives are already described in the US patent specification No. 4307072 with the general formula

.R,

, C0NHCH.C0l<

in which R, is hydrogen, lower alkyl, hydroxy-lower alkyl or poly-hydroxy lower alkyl.

In the final manufacturing step for the preparation of these compounds the dimethyl ester of the corresponding acid is converted with an amine of the type R,-NH-R2 into the diamide.

The simplest amines that can be used are 1-amino-2,3,-propanediol and 1-methylamine-2,3-propanediol.

Both the price of these amines and the rather low yield of purification, which is reported to be less than 60%, will increase the cost of manufacturing considerably.

If however the dimethyl ester is alowed to react with the cheap raw material diethano-lamine, the bis(diethanolamide is obtained in a high yield and a practically pure form, as described in the examples. The purification is easy and consist merely of washing the product with methanol in order to remove any adhering diethanol amine.

The invention therefore also relates to a process for the preparation of N,N,N'N'-tet-

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GB2 142 009A 2

ra(hydroxyethyl)-5-acetyIamino-2,4,6-triiodo-iso-phtaloxylglycinamide which is characterized in that 5-nitro-iso-phtaloxyglycine is reduced, the formed amino compound is iodi-5 nated, the formed triiodo compound is esteri-fied, the formed ester is acetylated and the acetylated ester is converted with diethano-lamino.

The compound is sparingly soluble in meth-10 anol but extremely well in water. Its solubility in water at room temperature is about 3 g/ml, much higher than needed for practical purposes.

Both the method of preparation and yields 15 of 5-acetylamino-2,3,6-triidoisophtaloyldigly-cine dimethyl ester, as described in the US patent specification 3102880 and 4307072, are considerably improved if esterification of the 5-amino-2,4,6-triidoisophtaloyldiglucine is 20 carried out first and acetylation of the dimethyl ester is carried out subsequently.

Surprisingly it also appears that no special purification of the intermediates is necessary, which also contributes to higher yields. The 25 diiodo by-products, present in the crude iodi-nation product, as a result of some steric hindrance, are for the greater part removed by the esterification procedure.

The remaining diiodo product and some 30 inevitable mono-ester is removed by the acetylation procedure.

The remaining mono-ester will be converted into mono-amide, which is completely removed in the amidification step.

35 By the procedure, as further explained in the examples, an excellent, water soluble, nonionic contrast agent is prepared at low cost, using simple and cheap raw materials in a rapid and simple way.

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EXAMPLE 1

1. Preparation of 5-amino-2,4,6-triidoiso-phtaloyldiglycine

73.12 g (225 mole) of 5-nitro-isophtaloyldi-45 glycine is dissolved in 1 I of water with ammonia to a pH = 7.5.

20 g of Raney nickel is added and the reduction carried out under hydrogen pressure at 20 atm.

50 The solution is filtered and diluted to 3 1.

150 ml 36% HCL is added and the solution is heated to 70°C.

525 ml 1.62 NalCL2 solution is added. A heavy precipitate is gradually formed. After 55 stirring for 20 hours at 70°C the crystalline product is filtered ans washed with bisulphite solution and water.

Yield: 131.5 g. Mol. wt. found: 640, theory: 673.

60 2. Preparation of 5-amino-2,4,5-triidoiso-phtaloyldiglycine dimethyl ester

202 g of the crude acid is refluxed for 6 hours and 1 I of methanol, containing 27 g HCL (0.75 N). Both acid and ester are insol-65 uble in methanol. The appearance of the suspension gradually changes. After 6 hours the suspension is filtered and washed with methanol. 198.5 g of an off-white product is obtained. Yield: 94%. Melting point: 254°C. A pure reference sample melts at 266°C. I%: 52.8%, theory: 54,35%. The product still contains about 10% diiodo compound, together with 3.5% of mono-ester.

3. Preparation of 5-acetylamino-2,4,6-trii-doisophtaloyldiglycine dimethyl ester

150 g of the crude amino ester is mixed with 300 ml of acetic acid and 75 ml of acetic anhydride. The suspension is stirred and heated to 95°C, 5 ml of sulphuric acid is added, upon which the temperature rises at once to 105°C. the mixture is stirred for another hour at 115°C and cooled. A rather thick suspension is obtained. This is filtered and washed with acetic acid until as much liquid has been collected as was used in the reaction. The crystalline mass is stirred in 400 ml of methanol and filtered. Finally the product is washed with methanol.

129.2 g of a perfectly white product is obtained. Yield: 81%

l%: 51.3%, theory: 51.3%. The product contains 2.5% of mono-ester.

4.Preparation of N,N,N',N'-tetra(hydroxye-thyl)-5-acetylamino-2,4,6-triidoisophtaloyldi-glycineamide.

100 g (1 34.6 mmole) of the di-ester and 100 g of 94% diethanolamine (896 mmol) are stirred at 85°C.

Initially the mixture is a thick suspension, which gradually becomes less viscous. After a short, transient dissolution, a viscous paste is formed. This paste is diluted with 100 ml of methanol and stirred until completion of the reaction. In order to control if the amidification reaction is finished, a small sample of the mixture is mixed with a few drops of water. This should give a clear solution. It takes about 8 hours to complete the reaction.

The mixture is diluted with 400 ml of methanol in order to facilitate the filtration and the removal of the excess of diethanolamine. The filtered product is suspended in 400 ml of methanol at 60°C and stirred for an hour, filtered and washed with methanol and the procedure repeated once more.

Yield: 107.7 g, 90.0%

l%: 42.8%, theory: 42.85%

alkalimetry: absence of mono-ami-de TLC: one spot

NMR spectrum: in compliance with the predicted structure.

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Example 2

Preparation of a solution, containing 300 mg l/ml

5 Composition:

tetra (hydroxyethyl)-5-acetylamino-2,4,6-triiodoisopthaloyl-diglycinamide

700,6 mg

10 tris (hydroxymethyi) aminomethane edetate calcium disodium hydrochloric acid

1 mg 0.7 mg

15 to pH 7.1

water for injection to 1 ml

The edtate calcium disodium is dissolved in 20 water for injection, then the iodo compound, tris(hydroxymethyl)aminomethane and hydrochloric acid to pH = 7.1. Water is added to weight or volume (d^°= 1.356). The solution is filtered through a millipore membrane 25 and finally the pH is checked again and adjusted if necessary. The solution is filled into ampoules and sterilized at 120°G fpr 20 minutes.

Claims (3)

30 CLAIMS

1. N,N,N',N'-tetra(hydroxyethl)-5-acetylamino-2,4,6-triiodoisophtaloyldiglyci-namide.

2. A process for the preparation of

35 N,N, N', N'-tetra(hydroxyethyl)-5-acetylamino-2,4,6-triiodoisophtaloyldiglycinamide, characterized in that 5-nitro-isophthaloyldiglycine is reduced, the formed amino compound is iodi-nated.the formed triiodocompound is esteri-40 fied, the formed ester is acetylated and the acetylated ester is converted with diethano-lamine.

3. X-ray contrast agent containing a tri-iodo compound characterized in that the tri-

45 iodo compound consists of N,N,N',N'-tetra(hy-droxyethyl)-5-acetylamino-2,4,6-triiodoisophta-loyldiglycinamide.

Printed in the United Kingdom for

Her Majesty's Stationery Office, Dd 8818935, 1985, 4235. Published at The Patent Office, 25 Southampton Buildings,

London. WC2A 1AY, from which copies may be obtained.